U2AF1 and myelodysplastic syndrome: U2AF1 mutations are found in ~15% of MDS patients without RARS, in ~10% of CMML, ~10% of s‐AML,15, 18, 68 ~10% of hairy cell leukemia variant (HCL‐v),75 and is generally associated with poor prognosis, and increased risk of leukemic transformation.